<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .div-f{
            width: 800px;
            height: 800px;
            background: red;
        }
        .div-s{
            height: 50%;
            width: 10%;

            /*height: 2cm;*/
            /*width: 2cm;*/
            background: #2fff3d;
        }

    </style>
</head>
<body>


    <div class="div-f">
        <div class="div-s">

        </div>
    </div>


</body>
</html>
